Backlight module

ABSTRACT

A backlight module includes a back bezel, a light guide plate, a plurality of optical films, and a clamping device. The light guide plate is disposed in an area enclosed by a periphery structure of the back bezel, and the optical films are disposed on the light guide plate. The clamping device includes a supporting element, a clamping piece, and a cushion element. The supporting element protrudes from the back bezel. The clamping piece is disposed on the supporting element and extends from the back bezel to the optical films. The cushion element is disposed between the clamping piece and the optical films.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 99128493, filed on Aug. 25, 2010. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of this specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a clamping device. More particularly, theinvention relates to a clamping device disposed on a backlight module.

2. Description of Related Art

In a liquid crystal display (LCD), a cold cathode fluorescent tube(CCFT) or a light emitting diode (LED) is often applied as a lightsource, and light emitted from the light source passes through a lightguide plate and is guided to a display frame. Optical films are requiredfor uniformizing the luminance of the LCD and maintaining the brightnessof the entire frame without diminishing the brightness of the lightsource is not reduced. Currently, the backlight modules mainly adoptoptical films (e.g., diffusers) to uniformize and concentrate the light.

However, during a vibration inspection on the backlight module or on theLCD, the optical films are apt to be scratched. Hence, the optical filmsare often suspended above the light guide plate to prevent movement ofthe optical films and thereby avoid scratches. Unfortunately, this leadsto limited effects in preventing the scratches. On the other hand, in aminiaturized LCD module which employs the LED as the light source, theoptical films and the light guide plate are rather close to each other,or the optical film are quite close to one another. Thus, the opticalfirms are more vulnerable to the scratches.

Given the optical films are firmly fixed, for example, by adhesion orthrough structural restriction, the optical films are prone to be wavybecause of an uneven force received by the optical films. As such,optical performance of the backlight module is deteriorated.

SUMMARY OF THE INVENTION

The invention is directed to a backlight module with favorabledurability.

An embodiment of the invention provides a backlight module that includesa back bezel, a light guide plate, a plurality of optical films, and aclamping device. The light guide plate is disposed in an area enclosedby a periphery structure of the back bezel. The optical films aredisposed on the light guide plate. The clamping device includes asupporting element, a clamping piece, and a cushion element. Thesupporting element protrudes from the back bezel. The clamping piece isdisposed on the supporting element and extends from the back bezel tothe optical films. The cushion element is disposed between the clampingpiece and the optical films.

According to an embodiment of the invention, the clamping piece is abi-material clamping piece that includes a first material and a secondmaterial, and the second material is located between the first materialand the cushion element.

According to an embodiment of the invention, a thermal expansioncoefficient of the second material is greater than a thermal expansioncoefficient of the first material.

According to an embodiment of the invention, the thermal expansioncoefficient of the first material ranges from about 1 μm/m° C. to about7 μm/m° C.

According to an embodiment of the invention, the thermal expansioncoefficient of the second material ranges from about 22 μm/m° C. toabout 30 μm/m° C.

According to an embodiment of the invention, the first material is afirst metal layer.

According to an embodiment of the invention, the first metal layer is aFe—Ni alloy layer.

According to an embodiment of the invention, the second material is asecond metal layer.

According to an embodiment of the invention, the second metal layer is aCu—Ni—Mn alloy layer or a Zn—Cu alloy layer.

According to an embodiment of the invention, a Young's modulus of thebi-material clamping piece ranges from about 100 GPa to about 180 GPa.

According to an embodiment of the invention, a thickness of thebi-material clamping piece ranges from about 0.5 mm to about 2 mm.

According to an embodiment of the invention, a material of the cushionelement is rubber or silica gel.

According to an embodiment of the invention, a friction coefficient ofthe cushion element ranges from about 0.5 to about 1.

According to an embodiment of the invention, the supporting element hasa through hole, and the bi-material clamping piece is locked onto theback bezel via a securing element that passes through the through hole.

According to an embodiment of the invention, the supporting element is abi-material supporting element that includes a third material and afourth material, and the fourth material is located between the thirdmaterial and the optical films.

According to an embodiment of the invention, a thermal expansioncoefficient of the fourth material is greater than a thermal expansioncoefficient of the third material.

According to an embodiment of the invention, the supporting element andthe clamping piece are integrally formed and include a fifth materialand a sixth material. The sixth material is located between the fifthmaterial and the optical films.

According to an embodiment of the invention, a thermal expansioncoefficient of the sixth material is greater than a thermal expansioncoefficient of the fifth material.

According to an embodiment of the invention, the thermal expansioncoefficient of the fifth material ranges from about 1 μm/m° C. to about7 μm/m° C.

According to an embodiment of the invention, the thermal expansioncoefficient of the sixth material ranges from about 22 μm/m° C. to about30 μm/m° C.

Based on the above, the clamping piece is made of the bi-material in theembodiments of the invention. Here, a portion of the clamping piececlose to the optical films has a thermal expansion coefficient greaterthan a thermal expansion coefficient of the other portion of theclamping piece away from the optical films. Therefore, when thebacklight module is moved or undergoes the vibration inspection undernormal temperature, the clamping piece can firmly secure the opticalfilms onto the light guide plate, so as to prevent scratches caused byrelative movement between the optical films and the light guide plate ormovement of the optical films. Moreover, when the backlight module isbeing operated, the clamping piece gradually releases the optical filmstogether with an increase in the temperature of the backlight module,e.g., from about 20° C. to about 70° C. Thereby, the optical films inthe operating backlight module are not deformed by the uneven force anddo not become wavy, which often happens according to the related art. Assuch, optical performance of the backlight module can be effectivelyimproved.

In order to make the aforementioned and other features and advantages ofthe disclosure comprehensible, embodiments accompanied with figures aredescribed in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1A is an exploded view illustrating a backlight module according toan embodiment of the invention.

FIG. 1B is a partially enlarged view of FIG. 1A.

FIG. 1C is a cross-sectional view illustrating the backlight moduledepicted in FIG. 1B after being assembled.

FIG. 2 is a schematic view illustrating a backlight module according toanother embodiment of the invention.

FIG. 3 is a schematic view illustrating a backlight module according tostill another embodiment of the invention.

DESCRIPTION OF EMBODIMENTS

FIG. 1A is an exploded view illustrating a backlight module according toan embodiment of the invention. FIG. 1B is a partially enlarged view ofFIG. 1A. FIG. 1C is a cross-sectional view illustrating the backlightmodule depicted in FIG. 1B after being assembled. Here, some componentsare asymmetrically enlarged for clear illustrations. With reference toFIG. 1A to FIG. 1C, in this embodiment, the backlight module 100includes a back bezel 110, a light guide plate 120, a plurality ofoptical films 130, and a clamping device 140. The light guide plate 120is disposed in an area enclosed by a periphery structure 114 of the backbezel 110, and the back bezel 110 can be made of metal or plastic. Theoptical films 130 are disposed on the light guide plate 120. Theclamping device 140 includes a supporting element 142, a clamping piece144, and a cushion element 146. The supporting element 142 protrudesfrom the periphery structure 114 of the back bezel 110, and thesupporting element 142 can be a metal protrusion or a plastic bump. Theclamping piece 144 is disposed on the supporting element 142 and extendsfrom the periphery structure 114 of the back bezel 110 to the opticalfilms 130. The cushion element 146 is disposed between the clampingpiece 144 and the optical films 130.

Note that the clamping piece 144 of this embodiment is a bi-materialclamping piece having an optimal thickness that ranges from about 0.5 mmto about 2 mm. Said optimal thickness range is determined based on therequired thickness of the backlight module. Excessive thickness of theclamping piece 144 results in insufficient space, and overly smallthickness of the clamping piece 144 leads to non-compliance with therequirements for deformation and strength. On the other hand, a Young'smodulus of the clamping piece 144 ranges from about 100 GPa to about 180GPa. The clamping piece 144 includes a first material 144A and a secondmaterial 144B. The second material 144B is located or directly connectedbetween the first material 144A and the cushion element 146, and is alsolocated between the first material 144A and the optical films 130. Thefirst material 144A and the second material 144B both have a layer-likestructure. A thermal expansion coefficient of the second material 144Branges from about 22 μm/m° C. to about 30 μm/m° C., and the secondmaterial 144B is a Cu—Ni—Mn alloy layer or a Zn—Cu alloy layer, forinstance. A thermal expansion coefficient of the first material 144Aranges from about 1 μm/m° C. to about 7 μm/m° C., and the first material144A is a Fe—Ni alloy layer, for instance. The first material 144A andthe second material 144B are not limited to metal or alloys. Since thethermal expansion coefficient of the second material 144B is greaterthan the thermal expansion coefficient of the first material 144A, thedeformation of the clamping piece 144 caused by temperature allows theclamping piece 144 to clamp or release the optical films 130. That is tosay, the first material 144A and the second material 144B are mainlyselected from materials that have relatively significant deformation andcan supply a sufficient fixing force within the same temperature range,e.g., 20° C.˜70° C.

In this embodiment, according to the information of the bi-materialalloy provided by Eastern Union Co., Ltd., the first material 144A andthe second material 144B can be combined through a liquid-solidcomposite process, such as a casting process, a hot-pip galvanizedprocess, a spray forming process, a thermal spray process, and so forth.The bi-metal alloy can also be formed by a solid-solid compositeprocess, such as a diffusion bonding process, an explosion bondingprocess, a clad roll bonding process, and so on. The method of formingthe bi-material alloy is not limited herein.

Given the backlight module 100 is not operated and is under normaltemperature, the clamping piece 144 firmly secures the optical films 130onto the light guide plate 120 in a first direction D1. Accordingly, nomatter the backlight module 100 is moved or undergoes the vibrationinspection, the optical films 130 can be fixed between the clampingpiece 144 and the light guide plate 120, so as to prevent the scratchescaused by movement of the optical films 130 according to the relatedart. On the other hand, when the backlight module 100 is being operated,the temperature of the backlight module 100 is gradually increased (forinstance, from 20° C. to 70° C.), and the thermal deformation of thesecond material 144B is more significant than the thermal deformation ofthe first material 144A. The clamping piece 144 is thus deformed littleby little in a second direction D2 opposite to the first direction D1,and the optical films 130 are released. Thus, when the backlight module100 is being operated, the optical films 130 are not deformed by theuneven force and do not become wavy, which often happens according tothe related art. As such, optical performance of the backlight module100 can be effectively improved.

Additionally, in this embodiment, the cushion element 146 is made ofsoft materials, e.g., rubber or silica gel, so as to prevent the opticalfilms 130 from being scratched. A friction coefficient of the cushionelement 146 ranges from about 0.5 to about 1, and therefore anappropriate friction force supplied by the cushion element 146 and anormal force provided by the clamping piece 144 are applied to firmlyclamp the optical films 130.

Besides, in this embodiment, the supporting element 142 has a firstthrough hole B1, and the clamping piece 144 has a second through holeB2. The clamping device 140 can further include a securing element 148.The clamping piece 144 is locked onto the back bezel 110 by the securingelement 148 that passes through the first and the second through holesB1 and B2 and lodged into a securing hole 112 of the back bezel 110. Thestructure of the securing element 148 by which the clamping piece 144 islocked onto the back bezel 110 is not limited in this embodiment. Thesecuring element 148 can be a screw, a pin, or any other fixing element.In this embodiment, the supporting element 142 is independent from theback bezel 110, while the supporting element 142 and the back bezel 110in another embodiment of the invention can be integrally formed. Forinstance, the supporting element 142 can be a protrusion formed bypunching and molding the back bezel 110.

FIG. 2 is a schematic view illustrating a backlight module according toanother embodiment of the invention. In this embodiment, a clampingdevice 240 includes a supporting element 242, a clamping piece 244, acushion element 246, and a securing element 248. Different from theprevious embodiment, this embodiment provides the supporting element 242which is a bi-material supporting element and is fixed onto the backbezel 110 by the securing element 248. The supporting element 242includes a third material 242A and a fourth material 242B. The fourthmaterial 242B is located between the third material 242A and the opticalfilms 130, and is also located between the third material 242A and theoptical films 130. The third material 242A has a layer-like or aplate-like structure, and the fourth material 242B has an L-shapedstructure. In this embodiment, the clamping piece 244 is adhered orlocked onto at least one of the third material 242A and the fourthmaterial 242B, while the clamping piece in another embodiment (notshown) can be merely connected to the third material or the fourthmaterial. Moreover, in another embodiment (not shown), the clampingpiece and the third material can be integrally formed, or the clampingpiece and the fourth material can be integrally formed.

According to this embodiment, a thermal expansion coefficient (rangingfrom about 22 μm/m° C. to about 30 μm/m° C.) of the fourth material 242Bis greater than a thermal expansion coefficient (ranging from about 1μm/m° C. to about 7 μm/m° C.) of the third material 242A. When thebacklight module 200 is being operated, the rising temperature allowsthe supporting element 242 to deform the clamping piece 244 in a thirddirection D3, so as to release the optical films 130. Effects achievedin this embodiment can also be accomplished in the previous embodiment.Besides, in this embodiment, material costs can be reduced, and easyassembly is achieved.

FIG. 3 is a schematic view illustrating a backlight module according tostill another embodiment of the invention. In this embodiment, aclamping device 340 includes a clamping structure 341, a cushion element346, and a securing element 348. Different from the previous embodiment,this embodiment provides the clamping structure 341 of which thesupporting element and the clamping piece are integrally formed. Theclamping structure 341 includes a fifth material 341A and a sixthmaterial 341B. The sixth material 341B is located or directly connectedbetween the fifth material 341A and the cushion element 346, and is alsolocated between the fifth material 341A and the optical films 130. Thefifth material 341A has an L-shaped structure, and the sixth material341B has a U-shaped structure. Here, the sixth material 341B is similarto the second material 144B of the embodiment depicted in FIG. 1A or thefourth material 242B of the embodiment depicted in FIG. 2, and the fifthmaterial 341A is similar to the first material 144A of the embodimentdepicted in FIG. 1A or the third material 242A of the embodimentdepicted in FIG. 2. Therefore, the optical films 130 in the backlightmodule 300 of this embodiment, as those in the backlight modules 100 and200 of the previous embodiments, can be firmly fixed.

In light of the foregoing, a portion of the bi-material clamping piececlose to the optical films has a thermal expansion coefficient greaterthan a thermal expansion coefficient of the other portion of theclamping piece away from the optical films according to the embodimentsof the invention. Therefore, when the backlight module is moved orundergoes the vibration inspection under normal temperature, theclamping piece can firmly secure the optical films onto the light guideplate, so as to prevent scratches caused by relative movement betweenthe optical films and the light guide plate or movement of the opticalfilms. Moreover, when the backlight module is being operated, theclamping piece gradually releases the optical films together with anincrease in the temperature of the backlight module. Thereby, theoptical films in the operating backlight module are not deformed by theuneven force and do not become wavy, which often happens according tothe related art. As such, optical performance of the backlight modulecan be effectively improved.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosure withoutdeparting from the scope or spirit of the disclosure. In view of theforegoing, it is intended that the disclosure cover modifications andvariations of this disclosure provided they fall within the scope of thefollowing claims and their equivalents.

What is claimed is:
 1. A backlight module comprising: a back bezelhaving a periphery structure; a light guide plate disposed in an areaenclosed by the periphery structure of the back bezel; a plurality ofoptical films disposed on the light guide plate; and a clamping devicecomprising: a supporting element protruding from the back bezel; aclamping piece comprising a plurality of stacked layers, disposed on thesupporting element and extending from the back bezel to the opticalfilms; and a cushion element disposed between the clamping piece and theoptical films, wherein the clamping piece comprising the stacked layersis a bi-material clamping piece and comprises: a first material layer,wherein the first material layer is a first metal layer; and a secondmaterial layer located between the first material layer and the opticalfilms, wherein the second material layer is a second metal layerdifferent from the first metal layer.
 2. The backlight module as claimedin claim 1, wherein a thermal expansion coefficient of the secondmaterial layer is greater than a thermal expansion coefficient of thefirst material layer.
 3. The backlight module as claimed in claim 2,wherein the thermal expansion coefficient of the first material layerranges from about 1 μm/m° C. to about 7 μm/m° C.
 4. The backlight moduleas claimed in claim 2, wherein the thermal expansion coefficient of thesecond material layer ranges from about 22 μm/m° C. to about 30 μm/m° C.5. The backlight module as claimed in claim 1, wherein the first metallayer is a Fe—Ni alloy layer.
 6. The backlight module as claimed inclaim 1, wherein the second metal layer is a Cu—Ni—Mn alloy layer or aZn—Cu alloy layer.
 7. The backlight module as claimed in claim 1,wherein a Young's modulus of the bi-material clamping piece ranges fromabout 100 GPa to about 180 GPa.
 8. The backlight module as claimed inclaim 1, wherein a thickness of the bi-material clamping piece rangesfrom about 0.5 mm to about 2 mm.
 9. The backlight module as claimed inclaim 1, wherein a material of the cushion element is rubber or silicagel.
 10. The backlight module as claimed in claim 1, wherein a frictioncoefficient of the cushion element ranges from about 0.5 to about
 1. 11.The backlight module as claimed in claim 1, wherein the supportingelement has a through hole, and a bi-material clamping piece is lockedonto the back bezel by a securing element passing through the throughhole.